PEG/(NH_4)_2SO_4双水相相平衡数据的关联及木瓜蛋白酶在该体系中分配模型的建立

Correlation of PEG/(NH_4)_2SO_4 Aqueous Two-phase Equilibrium Data and Modeling of Partition of Papain

为了研究木瓜蛋白酶在双水相中的分配行为,用浊点法测定了聚乙二醇(2000、4000、6000)/硫酸铵双水相体系在298.15K下的双节线和液液相平衡数据,采用Merchuk方程、Othmer-Tobisa方程和Bancroft方程对双节线数据、液液相平衡数据进行了关联,并建立了木瓜蛋白酶在PEG/(NH4)2SO4双水相体系中的分配模型。通过相关系数考察双水相各组分浓度与分配系数的相关度,得到分配系数的对数与上下相组分的浓度差相关度较高,提出了木瓜蛋白酶分配系数与双水相成相组分浓度差的经验关系式,木瓜蛋白酶分配系数的计算值与实验值之间的相对偏差小于10%且小于其他同类模型,表明实验建立的模型对木瓜蛋白酶在聚乙二醇(2000、4000、6000)/硫酸铵双水相体系中关联效果较好,可用于木瓜蛋白酶分配系数的计算,为双水相体系中木瓜蛋白酶酶活分配系数的工程计算和双水相萃取过程的设计提供参考。

In order to investigate the partition of papain in aqueous two-phase systems, the liquid-liquid phase equilibrium data of the aqueous two-phase systems containing poly（ethylene glycol）（2000, 4000, 6000） /ammonium sulfate was measured by cloud point measurements at T=298.15 K. The experimental binodal data and liquid-liquid phase equilibrium data were correlated using the Merchuk, Othmer-Tobisa, and Bancroft equations. A model was established to describe the partition of papain in the PEG/（NH4）2SO4 aqueous two-phase system. The degree of correlation between the component concentrations and partition coefficients in different groups of the aqueous two-phase system was examined using relevant coefficients. The logarithm of the partition coefficient and the concentration difference between the two-phase components had a relatively high correlation; meanwhile, an empirical equation describing the papain partition coefficient and concentration difference between the aqueous two-phase components was developed. The mean relative deviation between the experimental and calculated papain partition coefficients was less than 10%, and was also less than the values from similar models. This confirmed that the established model revealed a good correlation between papain in PEG/（NH4）2SO4 aqueous two-phase system and could be used for calculation of papain partition coefficients. The result provided references for engineering calculations of papain partition coefficients in aqueous two-phase systems and design of aqueous two-phase extraction processes.